Quality Control, Defect Identification and Rectification
This final domain tests inspection: knowing what acceptable work looks like, naming a defect correctly, and fixing it so it does not come back.
What to check
- Flatness and level against the specification, checked with a straightedge and level, not by eye.
- Lippage between adjacent tiles, joint width consistency, alignment of joints and pattern.
- Bond: tap tiles with a mallet handle or tap rod; a dull, hollow sound means voids.
- Grout: full joints, even colour, clean edges, no pinholes or cracks.
- Falls to drains, perimeter gaps, movement joints, and the finish of cuts around fittings.
Common defects and causes
- Drummy or hollow tiles: insufficient coverage, skinned adhesive, dusty substrate.
- Lippage: uneven substrate, tile warpage, no clips.
- Tenting or lifting at joints: no movement provision.
- Cracks: substrate movement or impact.
- Efflorescence and staining: moisture, wrong cleaning agents, unsealed stone.
- Shade variation: mixed batches not checked at delivery.
Worked example
A 600×600 floor tile sounds hollow at one corner. Tap the neighbours: if they ring solid, the problem is local. Remove and replace the tile - injecting adhesive into a thin-set void is unreliable and will not restore full contact. Record it on the punch list with location and cause, replace with a tile from the same batch, regrout, and recheck. Reasoning: a hollow tile in a walkway will loosen and crack; fixing it once is cheaper than returning.
Traps that cost marks
- Judging flatness by eye or by standing on the tiles.
- Smearing grout over a lipped edge to hide it.
- Not recording tile batch or shade at delivery.
- Leaving the punch list until after handover, when access is gone.